Digging Into Power Draw
On any system there are always various components drawing power at all times. The display is generally the highest power consumer on any system at idle, and the amount of energy it draws varies on the size, brightness, and resolution. For instance, the display of a Surface Book 2 15-inch draws about 7.65 Watts at 100% brightness. Setting the display down to 200 nits drops its power draw to 4.1 Watts. Meanwhile the rest of the system pulls just 1.43 Watts at idle.
Raven Ridge, it appears, has a power draw problem. We saw it on the Acer Swift 3, and we’re seeing it again on the Lenovo ThinkPad A285. The base power draw is quite high, which makes the battery deplete much more quickly than it should. Let’s look at some numbers:
For this test, we've set the display to 100% brightness while the rest of the system is idling, with Windows set to shut off the display after a couple of minutes. The graph above includes both the Surface Book 2 (Green/Blue) and the ThinkPad A285 (Red), plotting the total power draw of each system. Since the display itself is only on for a couple of minutes, the first part of the graph is with the display at 100%, while the remaining section of the graph shows the system's average idle power draw.
Breaking things down, we see that the ThinkPad A285 starts out with an average power draw of 8.62 Watts with its display on and the system idling. Waiting a few minutes for the display to turn off, and we see that the average system power consumption drops by just over 4 Watts to 4.6 Watts. This is a significant drop, but not significant enough. The Surface Book 2 in the same scenario idles at a little more than one-third of this, meaning the A285 – and specifically, the Raven Ridge platform inside – is drawing an additional 3 watts at full idle. This is a huge amount of power to draw at idle, and leads to the less than amazing battery life results on Raven Ridge devices.
Some of the draw will be from the DDR4 memory, since most Ultrabooks leverage LPDDR3 to reduce the power usage, but that is not going to be all of it. It looks like AMD has some work to do in order to get its power usage in check if they want to better compete in the laptop space. They need their
Haswell moment.